Light emitting diodes (hereinafter referred to as “LEDs”) is currently one of the most innovative and fastest growing technologies in the semiconductor industry. While LEDs have been in use for decades as indicators and for signaling purposes, technology developments and improvements have allowed for a broader use of LEDs in illumination applications.
The use of LEDs in illumination applications is attractive for a number of reasons, including the ability to produce more light per watt, a longer lifetime, smaller sizes, greater durability, environmental friendliness, and flexibility in terms of coloring, beam control, and dimming.
The main applications of LED luminaries are LCD backlighting, white light illumination, mood lighting and automotive lighting. It is known that the optical characteristics of LED luminaries, especially the red LEDs, vary greatly with changes in environmental temperature. Accordingly, the luminous intensity, CRI (color rendering index), CCT (correlated color temperature) and chromaticity values of LED luminaries used in a cold climate will differ from those of the same LED luminaries used in a warmer climate. Therefore, one major problem with LED luminaries in illumination applications is providing a consistent and expected optical performance that does not vary with changes in environmental temperature.
Earlier attempts have been made to detect the temperature of the LEDs and then make adjustments by an external power supply to maintain the performance consistency of the LED module. However, the previous efforts have had the following shortcomings: the form factor of the LED module cannot be very small; the response time is slow and not accurate enough because the distance between the temperature detection unit and the LED is large; the light of the LED is obstructed; calibration is needed for each LED module; and soldering perform hierarchy problem exists. As a result, the above functional, performance and cost limitations have failed to provide an effective LED module. Accordingly, there is a need for a light emitting device package that addresses these and other shortcomings of LED modules.